1. Field of the Invention
The present invention relates to a swash plate compressor, and more particularly, to a swash plate compressor having an improved structure for preventing rotation of a race in the compressor.
2. Description of the Related Art
In an air conditioning apparatus for an automobile, a typical compressor enables refrigerant to continuously circulate by sucking heat exchange medium vaporized in an evaporator, compressing the sucked heat exchange medium, and pumping the compressed heat exchange medium. The compressor is classified into various types such as a swash plate type, a scroll type, a rotary type, and a wobble plate type based on a driving method.
FIG. 1 shows an example of a swash plate type compressor 100. Referring to the drawing, the swash plate type compressor 100 includes a plurality of pistons 112 installed in a cylinder block 111 to be inserted therein and a drive shaft 113 is installed at the central portion of the cylinder block 111. A boss 112a having a shoe pocket (not shown) for accommodating a shoe (not shown) to facilitate smooth sliding of the pistons 112 with respect to a swash plate 114 is formed in the middle portion of each of the pistons 112. Since the swash plate 114 coupled to the drive shaft 113 is inserted in the boss 112a, when the swash plate 114 rotates, the pistons 112 can sequentially reciprocate in the lengthwise direction of the cylinder block 111.
A thrust bearing 120 is installed so that rotational movements of the swash plate 114 is converted to reciprocating movements of the pistons 112 at both sides of the swash plate 12.
Races 121a and 121b are interposed between the swash plate 114 and the thrust bearing 120, and a thrust surface 111c (see FIG. 2A) and the thrust bearing 120, respectively, at both sides of the thrust bearing 120. The races 121a and 121b guide needle type rollers 120a in the thrust bearing 120.
A valve plate 115 where suction holes 115a and discharge holes 115b are formed is installed at both sides of the cylinder block 111. A thin plate type suction reed 116 for opening and shutting the suction holes 115a and an discharge reed 117 for opening and shutting the discharge holes 115b are installed at both sides of the valve plate 115. A front head 118 and a rear head 119 are installed at both sides of the cylinder block 111 where the suction reed 116 and the discharge reed 117 are installed.
In the typical swash plate type compressor having the above structure, when the drive shaft 113 is rotated by a predetermined driving means (not shown), the swash plate 114 installed at the drive shaft 113 rotates so that the pistons 112 radially arranged at the cylinder block 111 are reciprocated. As the pistons 112 reciprocate, heat exchange medium is sucked and discharged while being compressed. Here, the suction reed 116 and the discharge reed 117 open and shut the suction holes 115a and the discharge holes 115b, respectively, by the pressure of the sucked or compressed heat exchange medium.
However, during the operation of the above swash plate type compressor 100, when an impact is generated by an instantaneous thrusting force, the races 121a and 121b are elastically deformed and absorb the impact. Here, by the instantaneous elastic deformation by the impact, an insertion phenomenon that the thrust bearing 120 is instantaneously inserted between the races 121a and 121b and the cylinder block 11 occurs. Then, the roller 120a in the thrust bearing 120 does not rotate due to the insertion phenomenon and the race 121b rotates together with the thrust surface 111c of the cylinder block 111 while making friction therebetween.
Meanwhile, the race 121a at the right contacting a thrust surface of the swash plate 114 hardly generates rotation and abrasion due to the rotation. This is because the right race 121a contacts the thrust surface of the swash plate 114 in a large area while the left race 121b contact the thrust surface 111c of the cylinder block 111 in a small area.
Due to the above phenomenon, the thrust surface 111c of the cylinder block formed of a relatively softer material is excessively abraded so that the gap between the swash plate 114 and the cylinder block 111 is generated and parts subordinately affected generate noise inside the compressor. Also, since the performance of the races 121a and 121b guiding the roller 120a of the thrust bearing 120 deteriorates, the thrust bearing 120 cannot properly absorb an impact and generates noise and further the thrust bearing 120 itself is damaged. Furthermore, as the swash plate 114 freely moves, the suction reed 116 is damaged as the pistons 112 apply impacts to the suction reed 116.
To solve the above problem, an swash plate type compressor is disclosed in Japanese Utility Model Publication No. 57-134370 (published on Aug. 21, 1982). In this swash plate type compressor, a protrusion for preventing rotation which is bent toward a cylinder block is installed at the outer circumferential surface of a race. The rotation preventing protrusion is inserted in a bore formed in the cylinder block to prevent the rotation of the race.
However, in the above swash plate compressor, since only one rotation prevention protrusion is provided, directivity is produced when the cylinder block and the race are coupled together and assembly thereof becomes difficult. Thus, when misassembly occurs, the piston may be damaged. Also, since there is an accommodating structure in which the protrusion of the race is inserted into the bore, excessive movements of the race may generate noise and as the inner surface of the bore and the protrusion may collide, foreign materials may be generated.
To solve the above-described problems, it is an object of the present invention to provide a swash plate type compressor having a race on the outer circumference surface of which at least two protrusions for preventing rotation are formed, so that, when the race is coupled to the cylinder block, the accommodating structure for preventing rotation by distributing a rotational force of the race and assembly thereof is improved.
To achieve the above object, there is provided a swash plate type compressor comprising a drive shaft rotated by a driving source, a swash plate fixedly installed at the drive shaft, a piston reciprocated by the swash plate, a cylinder bore, where the piston is installed to be capable of sliding, for guiding reciprocation of the piston, a thrust bearing supporting a thrust force generated the swash plate and the drive shaft, a race having a protrusion for preventing rotation radially formed at an outer circumference thereof, and a cylinder block having a protrusion fixing means for preventing rotation of the race by fixing the protrusion of the race. Thus, abrasion due to rotational friction between the flat surface of the race and the thrust surface of the cylinder block can be prevented.
It is preferred in the present invention that the protrusion fixing means is at least one pair of protrusion stoppers formed to face each other around a drive shaft insertion hole of the cylinder block.
It is preferred in the present invention that the protrusion fixing means is at least a protrusion insertion hole formed around the drive shaft insertion hole of the cylinder block.
It is preferred in the present invention that at least two protrusions for preventing rotation are fixedly supported at the protrusion fixing means of the cylinder block.
It is preferred in the present invention that the protrusion for preventing rotation is formed at an identical interval.